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Search: id:A140505
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| A140505 |
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Second differences of Jacobsthal sequence A001045, pairs with even and odd indices swapped. |
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+0
4
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| 2, -1, 4, 0, 12, 4, 44, 20, 172, 84, 684, 340, 2732, 1364, 10924, 5460, 43692, 21844, 174764, 87380, 699052, 349524, 2796204, 1398100, 11184812, 5592404, 44739244, 22369620, 178956972, 89478484, 715827884, 357913940, 2863311532, 1431655764, 11453246124
(list; graph; listen)
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OFFSET
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0,1
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COMMENT
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The second differences are -1, 2, 0, 4, 4, 12, 20, 44, ... (-1)^(n+1)*A084247(n), essentially A097073, which are listed here with -1 <=> 2, 0 <=> 4 etc. swapped in pairs.
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FORMULA
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a(n) = 4*A092808(n-2), n>1.
a(n+1) - 2a(n) = (-1)^n*A140504(n).
O.g.f.: (2+x-5x^2)/[(1+x)(1-2x)(1+2x)]. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 08 2008
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CROSSREFS
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Sequence in context: A077979 A122161 A067164 this_sequence A117971 A131642 A070674
Adjacent sequences: A140502 A140503 A140504 this_sequence A140506 A140507 A140508
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KEYWORD
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sign,less
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AUTHOR
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Paul Curtz (bpcrtz(AT)free.fr), Jun 30 2008
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EXTENSIONS
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Edited by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 08 2008
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